NACA-ARR-4E31

Abstract

INTORDUCTION <br>The design of curved sheet panels to resist shear involves a consideration of several factors: the buckling resistance of the sheet, the stress at which buckling becomes permanent, and the strength which may be developed beyond the buckling limit by tension-field action. Although some experimental as well as theoretical work has been done on the buckling and tension-field phases of this problem, neither of these types of action appears to be very well understood. The problem is of sufficient importance from the standpoint of aircraft design, it is believed, to warrant further experimental investigation. This report presents the results of the first series of torsion tests of stiffened circular cylinders to be completed in connection with this study at Aluminum Research Laboratories. <br>In some respects the shear problem for curved sheet panels is similar to that for flat panels. The buckling resistance depends not only upon curvature and the proportions of panel but also upon the restraint provided at the edges The strength which may be developed by-yond the buckling limit depends upon the capacity of the sheet to transmit shear by diagonal tension and the resistance of the stiffener system to such tensile forces. The suddenness with which buckling generally occurs in a curved sheet would appear to make this action more determinate by experimental methods than is the case inflate sheet where the effects of eccentricities of loading usually obscure well-defined buckling phenomena. Tension field action is more complex for curved panels, however, in that the stiffeners are subjected to combined bending and twist as well as axial compression. <br>Several solutions have been proposed for the problem of elastic shear-buckling in curved sheet panels. The ANC-5 Handbook (reference 1) indicates that this property may be determined by computing the critical stress for a first panel of the same proportions and adding a factor depending upon curvature. This solution is similar in form to that proposed by Wagner and Ballerstedt (reference 2) Kromm (reference 3) has derived an approximate formula for the stability limit of infinitely long curved plate strips; while Ebner (reference 4) indicates that this property may be determined by formulas similar to those developed for curved panels under compression Schapitz (reference 5) concludes that the shear-buckling action of curved sheet is largely unexplained. The latter reference presents the results of torsion tests of three stiffened circular cylinders and gives an analysis of tension-field action. Emphasis is placed upon the need for additional test, not only to indicate shear buckling characteristics, but to show the buckle patterns and stresses accompanying tension-field action.